This program initially developed laser microsurgical techniques for ophthalmological and cardiovascular applications (pulsed infrared lasers). Its primary focus has been the development of pulsed, solid-state infrared lasers for microsurgery. We demonstrated the feasibility of transmission through flexible fiber optics of pulsed IR, visible and UV lasers, and the tissue responses to these lasers. In particular, we have measured the dependence of acoustic transients and ablation efficiency on increasing pulse fluence with catheter systems used clinically, and have concluded that acoustic transients play a dominant role in the clinical results of pulsed laser angioplasty. New IR laser sources, which utilize strong water absorption and can be transmitted through low-loss, cladded optical fibers, were developed in conjunction with the Naval Research Lab and Quantronix Corporation. Clinical trials of peripheral and coronary laser angioplasty were completed using either pulsed-dye or pulsed infrared lasers with computer-controlled fluorescence guidance. Recent work has involved identification of the tissue and other biological effects of pulsed lasers, particularly the large role that acoustic transients and transient, moderate (about 60 degrees C) thermal elevations play in acute and chronic clinical responses. Since pulsed laser angioplasty principally disrupts the atheroma at stenoses mechanically rather than ablating or removing it, optimization of clinical results must be balanced against increased rates of dissection. Recently, a microsurgical laser microscope was developed for a variety of in vitro studies.